Recently, LTE-Advanced has been standardized as an extended version of LTE (Long Term Evolution) standardized in the 3GPP Releases 8 and 9. The LTE-Advanced specifications include a carrier aggregation technique. Carrier aggregation is a technique of sending and receiving signals simultaneously by aggregating a plurality of carrier waves of band blocks divided in widths of 20 MHz, each carrier wave being called a component carrier. There are two types of carrier aggregation: intra-band carrier aggregation uses an aggregate of component carriers in the same frequency band for transmission and reception, and inter-band carrier aggregation uses an aggregate of component carriers in different frequency bands for transmission and reception.
When the component carriers of different frequency bands are sent or received simultaneously, the front-end circuit of the portable terminal requires a mechanism for modulating and demodulating the carrier waves of the different frequency bands simultaneously, as shown in FIG. 1, for example. FIG. 1 is a block diagram showing the configuration of a conventional front-end circuit 90 that enables transmission and reception in multiple bands (first to N-th frequency bands, N being an integer not smaller than 2). As shown in FIG. 1, the front-end circuit 90 includes a transmission and reception antenna 91, a double-pole N-throw switch 92 with its common contact connected to the transmission and reception antenna 91, duplexers 93-1 to 93-N which receive the transmission and reception signals in the first to N-th frequency bands, with their common contacts connected respectively to the N changeover contacts of the switch 92, low-noise amplifiers 94-1 to 94-N which are connected to the reception terminals of the duplexers 93-1 to 93-N and amplify the reception signals in the first to N-th frequency bands, amplifiers 95-1 to 95-N which are connected to the transmission terminals of the duplexers 93-1 to 93-N and amplify the transmission signals in the first to N-th frequency bands, and an RFIC 96 which has transmission ports Tx1 to TxN for the first to N-th frequency bands and reception ports Rx1 to RxN for the first to N-th frequency bands. Since two frequency bands, namely, a primary component carrier and a secondary component carrier, allocated by a base station are used simultaneously, the switch 92 can connect two duplexers corresponding to the allocated component carriers and the transmission and reception antenna 91. For example, patent literature 1 discloses a front-end circuit which implements multiband transmission and reception.